SFF is typically used in design-related fields where it is used for visualization, demonstration and mechanical prototyping. Thus, in three-dimensional fabrication facilitates rapid fabrication of functioning prototypes with minimal investment in tooling and labor may be employed. Such rapid prototyping shortens the product development cycle and improves the design process by providing rapid and effective feedback to the designer. Three-dimensional fabrication can also be used for rapid fabrication of non-functional parts, e.g., for the purpose of assessing various aspects of a design such as aesthetics, fit, assembly and the like. Additionally, three-dimensional fabrication techniques have been proven to be useful in the fields of medicine, where expected outcomes are modeled prior to performing procedures. It is recognized that many other areas can benefit from rapid prototyping technology, including, without limitation, the fields of architecture, dentistry and plastic surgery where the visualization of a particular design and/or function is useful.
Over the past decade, there has been considerable interest in developing computerized three-dimensional fabrication techniques.
In one such technique, see, e.g., U.S. Pat. No. 6,259,962, a material is dispensed from a printing head having a set of nozzles to deposit layers on a supporting structure. The layers are then cured using a suitable curing device. It is further noted that in the conventional art printing viscous material with a resolution below 40 μm is relatively complex.
Additionally, the conventional art has a problem of oxygen inhibition that may occur in, for example, the curing of a monomer. In this regard, oxygen inhibition may hinder significantly or can even stop the curing process. For this reason, it is relatively complex to cure plastic in atmospheric environment; and therefore, a special inert gas environment is required.
Molecular oxygen can physically quench the triplet state of the photo-initiator/sensitizer, or it can attract free radicals or active radical centers and transform them into unreactive peroxide radicals. The end result may range from reduced coating properties to uncured, liquid surfaces on the coating. The aforementioned problem is even more pronounced in low intensity curing processes, such as UV LED or UVA cure, which frequently result in sticky, uncured surfaces.
In another technique, see, e.g., in U.S. Pat. No. 5,204,055, a component is produced by spreading powder in a layer and then depositing a binder material at specific regions of a layer as determined by the computer model of the component. The binder material binds the powder both within the layer and between adjacent layers. In a modification of this approach, the powder is raster-scanned with a high-power laser beam which fuses the powder material together. Areas not hit by the laser beam remain loose and fall from the part upon its removal from the system.
In an additional technique, see, e.g., in U.S. Pat. No. 4,575,330, a focused ultraviolet (UV) laser scans the top of a bath of a photopolymerizable liquid material. The UV laser causes the bath to polymerize where the laser beam strikes the surface of the bath, resulting in the creation of a solid plastic layer just below the surface. The solid layer is then lowered into the bath and the process is repeated for the generation of the next layer, until a plurality of superimposed layers forming the desired part is obtained.